1. Field of the Invention
The present invention relates to low color epoxy resin compositions and the use of such compositions in light emitting diodes (LEDs).
2. Description of Background and Related Art
The field of optoelectronics is poised for explosive growth as optoelectronic devices such as light emitting diodes (LEDs) have expanded their applications into various display and lighting applications including signal lamps, full-color displays, and other lighting apparatus.
Certain epoxy resin materials have excellent optically transmissive, mechanical, and adhesion properties. For example, cycloaliphatic epoxies find special utility as encapsulants or coatings to house and protect the LEDs. However, conventional epoxy resin materials usually suffer from drawbacks such as color formations caused by heat and light generated from light emitters in the LEDs, resulting in a color degradation of the LED light outputs and shortening the service life of the LEDs.
Glycidyl-ether-containing epoxies, particularly those containing an aromatic moiety, can also suffer from increased color formation upon storage at elevated temperatures. In addition, these epoxies may also experience in increase in viscosity upon storage at elevated temperatures. A diglycidyl ether derived from an aromatic bisphenol compound (e.g., bisphenol A) is commonly referred to as a “liquid epoxy resin” or LER.
There is a need in the industry to develop a low color cyclic- or alicyclic-containing epoxy resin composition for use as an encapsulant or as a coating in LEDs in order to provide improved thermal stability, to reduce the rate of heat aged color formation, and to prolong the service life of LEDs. There is also a need to improve the storage stability of glycidyl-ether-containing epoxy resins.